Hydrovac units have logged untold millions of miles, stopping max gross weight loads (or more accurately, big overloads) for several decades. Why mess with success? Just rebuild the brakes and steering systems to "as new" condition and drive on. "New" and "Modern" doesn't always equal "Better", particularly if you don't happen to be an automotive engineer with millions of dollars' worth of research and development budget at your disposal.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!